Hello, I’m Nathan, and I’ll be assisting you today. My livelihood depends on your positive feedback, so your satisfaction is my highest priority.
Sorry to hear you’re having trouble.
Your pbx system supports a small backup battery to preserve internal memory. The battery may be removed/disconnected, or just can no longer hold a charge, which wouldn't be surprising to see as this is a very old model. The battery is connected to a port on the lower right corner of the pbx. You may order a new one here: http://amzn.to/1MabN3i
It would also be highly advised to connect the system to a UPS system for redundancy: http://amzn.to/1Gvu8M0